GROMACS version: 2018.1

GROMACS modification: Yes/No

**I have a system with more than 100,000 atoms. After minimization using the following parameters:**

; minim.mdp - used as input into grompp to generate em.tpr

; Parameters describing what to do, when to stop and what to save

integrator = steep ;CG ; Algorithm (steep = steepest descent minimization)

;define = -DPOSRES

emtol = 100.0 ; Stop minimization when the maximum force < 1000.0 kJ/mol/nm

emstep = 0.01 ; Energy step size

nsteps = 2000 ; Maximum number of (minimization) steps to perform

; Parameters describing how to find the neighbors of each atom and how to calculate the interactions

nstlist = 10 ; Frequency to update the neighbor list and long range forces

ns_type = grid ; Method to determine neighbor list (simple, grid)

rlist = 1.2 ; Cut-off for making neighbor list (short range forces)

cutoff-scheme = verlet

coulombtype = PME ; Treatment of long range electrostatic interactions

rcoulomb = 1.2 ; Short-range electrostatic cut-off

rvdw = 1.2 ; Short-range Van der Waals cut-off

pbc = xyz ; Periodic Boundary Conditions

periodic-molecules = yes

**I got this result (See below). Kindly advise on how to get a system that satisfies -ve PE and Fmax < tolerance (emtol)**

Steepest Descents:

Tolerance (Fmax) = 1.00000e+02

Number of steps = 2000

Energy minimization reached the maximum number of steps before the forces

reached the requested precision Fmax < 100.

writing lowest energy coordinates.

Back Off! I just backed up em.gro to ./#em.gro.1#

Steepest Descents did not converge to Fmax < 100 in 2001 steps.

Potential Energy = -1.7481004e+07

Maximum force = 9.7902646e+03 on atom 11248

Norm of force = 2.4687517e+01

GROMACS reminds you: â€śEverything Must Goâ€ť (Red Hot Chili Peppers)